This disclosure involves a GC connector assembly. It is a device which is especially intended for use with tubing which connects a gas chromatograph (GC hereafter) to various pieces of test equipment. A gas chromatograph cannot work with a large fluid flow. Stated more precisely, most GC samples are extremely small samples. While it might be possible to obtain a test sample out of a large storage tank at a refinery, to pick an example, most laboratory investigations involve samples and specimens which are extracted from smaller and smaller sources. For instance, practically all biological work involves extracts from living tissue, not necessarily large samples at that. If a five or ten milliliter sample is initially provided, the extracted family of compounds of interest might be measured in the microliter range. To this end, a GC is scaled so that, while very small, it fortunately can provide high quality constituent separation with a throughput which is quite small. Literally, the separated volume is perhaps only parts per million of a sample in the microliter range so that the measured peak of interest output by the GC involves only a few hundred molecules of interest. That, indeed, is uncommonly small.
The GC equipment has to be hooked up to several items to operate. Commonly, there will be a pump for a flow of solvent. At the output end, the GC equipment will connect with some kind of analyzer such as an FID. Often, it will be output to any other small device for test purposes. The GC is normally built with valves, pumps, filters, and other equipment which are all connected together to upstream and downstream devices involving very small tubing and fittings. The tubing has a nominal size of 1/16 inch, which involves a diameter of 0.0625 inches. Commonly, it is made of stainless so that there is very little surface interaction between the metal of the tubing and the samples which flow through the tubing along with the carrier and discharge or waste gases. To this end, the system is quite small. Even in larger and more ambitious sizes, the tubing commonly will be 1/8 tubing which has an actual size of 0.125 inches. Whether it is either size tubing, the sidewall is normally formed of stainless steel for either size, and is made of sufficient thickness to have mechanical integrity.
Tubing of this sort is often connected and disconnected with the set of fittings to test equipment on the work bench. While an investigation may last only a day or two, and some other investigations will last many hundreds of experiments, the tubing on the work bench in a chemical test laboratory is plumbed to make the connections. These connections normally involve tubing of the sizes noted which connect with fittings. A common assembly technique involves the use of a male nut which is threaded behind a ferrule, and the nut, ferrule, and tubing end are positioned in a fitting detail. The term "detail" identifies an industry standard type of fitting which receives the threaded male nut with a mating set of threads, an internal tapered area for seating the ferrule, and an extending hole terminating in the shoulder. This receives the end of the tubing or the pilot portion of the tubing which extends into the detail. This is normally located in a larger device, being an internally formed cavity having the fitting detail in it. This will be at the base or input manifold of a valve assembly, or a larger assembly which involves the test device. This can be an input port on a pump, GC column base, GC input, input for a mass spectrometer and other test instruments. The fitting detail is often a counterbored assembly which is carefully fabricated so that the housing or manifold body receives the connections time and time again. Often, the fitting detail does not require refinishing for hundreds of connections spanning several years of use of the fitting detail and the structure to which it provides a port or input.
With as many connections and disconnections as are required, there is some risk of work hardening of the metal tubing. Localized stresses placed on the metal tubing are fairly severe to assure an adequate seal. While the total force involved may be small, taking into account the scale of the tubing, the localized stresses are fairly high. One of these stresses involves bending of the tube. In the optimum circumstance, the tube is input in a straight line fashion. However, optimum circumstances do not always happen. Moreover, the conditions that are involved in plumbing the thin tubing vary markedly so that all kinds of problems can arise. Representative plumbing problems include the difficulty of bending the tubing. Often, the fitting detail and nut in it will be jammed against a back splash on a test bench, or some other fixture which mandates that the tubing extend out of the fitting detail and nut, and then turn sharply at an angle. With the present apparatus, this can be done so that the tubing can extend against the back splash without damage. This significantly improves the plumbing and installation of a chemical test procedure equipment. This assists in a component location. This permits the plumed equipment to be jammed against the back splash without worry over damage or breakage of the tubing connections.